<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    #grid {
      display: grid;
      grid-template-columns: [start col-a] 200px [col-b] 50% [col-c] 100px [stop end last];
      grid-template-rows: [start masthead] 3em [content] calc(100% - 5em) [footer] 2em [stop end];
      background-color: antiquewhite;
      width: 600px;
      height: 300px;
    }
  </style>
</head>
<body>
  <div id="grid"></div>
</body>
</html>